1. Field of the Invention
The invention relates to a method for fabricating semiconductor device, and more particularly to a method of using two different cleaning agents to perform two separate wet clean processes on the dielectric layers above metal gate.
2. Description of the Prior Art
Along with the continuous miniaturization of the Integrated Circuits (IC), the line width of interconnections and the feature size of semiconductor devices have continuously shrunk. In general, discrete devices in integrated circuits are connected to each other through contact plugs (or contact slots) and interconnection structures, and their related fabrication methods have become an important matter in the next-generation semiconductor devices.
In current fabricating processes, due to the limitations of the back end of the line (BEOL) process capacity, the yield of contact plugs with high aspect ratio (HAR) is relatively low and cannot reach the new requirements. In order to overcome this drawback, a contact can be divided into two parts, a lower contact structure and an upper contact structure (i.e. the metal level zero, M0). After the lower contact structure is formed completely, the M0 is formed thereafter. The M0 can be a pole structure or a slot structure. However, as the upper contact structure (M0) and the lower contact structure are formed in different steps, a barrier layer is typically formed between the upper contact structure (M0) and the lower contact structure thereby affecting the conductivity of the contact and increasing the complexity of the entire fabrication process.
In order to overcome the aforementioned drawbacks, there is a need to provide a modified method for fabricating interconnection structures with better yields.